Solid state lamp using modular light emitting elements
A solid state lamp, such as one that can replace an incandescent light bulb, has a base portion having an electrical connector for connection to a source of power, such as an Edison-type connector for connection to the mains voltage. An AC/DC converter in the base converts the mains voltage to a suitable light emitting diode (LED) drive voltage. A plurality of receptacles on the base connects to electrodes of plug-in modules. Each plug-in module supports a plurality of low power LEDs connected in series. The strings of LEDs on different modules are connected in parallel when connected to the receptacles. The modules and base are configured to allow a user to operate the lamp with different combinations of modules to generate a desired light output from the lamp. For example, the user can recreate the lumens equivalent of a 20 W, 40 W, or 60 W bulb by using one, two, or three modules.
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This invention relates to a solid state lamp, such as a lamp using light emitting diodes (LEDs), and, in particular, to a solid state lamp whose light output is selectable and replaceable.BACKGROUND
A huge market for LEDs is in replacement lamps for standard, screw-in incandescent light bulbs, commonly referred to as A19 bulbs, or less formally, A-lamps. The letter “A” refers to the general shape of the bulb, including its base, and the number 19 refers to the maximum diameter of the bulb in eighths of an inch (e.g., 2⅜″ diameter). Such a form factor is also specified in ANSI C78-20-2003. Therefore, it is desirable to provide an LED lamp that has the same screw-in base as a standard light bulb and approximately the same size diameter or less. Additional markets exist for replacing other types of standard incandescent bulbs with longer lasting and more energy efficient solid state lamps.
Typical LED lamps having an A-shape use high power LEDs in order to use as few LEDs as possible to achieve the desired lumen output (e.g., 600-1000 lumens). Such LEDs may each draw a current greater than 300 mA and dissipate 1 W or more. Since the LED dies are on the order of about 1 mm2, adequate heat removal is difficult. The high power LED junction temperatures should typically be kept under 125° C. to ensure the LEDs remain efficient and have a long life. A common design is to mount high power LEDs on a flat, heat conductive substrate and provide a diffusive bulb-shaped envelope around the substrate. The power supply is in the body of the lamp. Removing heat from such designs, using ambient air currents, is difficult since the lamp may be mounted in any orientation. Metal fins or heavy metal heat sinks are common ways to remove heat from such lamps, but such heat sinks add significant cost and have other drawbacks. It is common for such LED replacement lamps to cost $30-$60. Additionally, the light emission produced by such a solid state bulb is unlike that of an incandescent bulb since all the LEDs are mounted on a relatively small flat substrate. This departure from the standard spherical distribution patterns for conventional lamps that are replaced with LED replacement lamps is of particularly concern to the industry and end users, since their existing luminaires are often adapted to spherical light emission patterns. When presented with the typical “hemi-spherical” type emission from many standard LED replacement lamps, there are often annoying shadow lines in shades and strong variations in up/down flux ratios which can affect the proper photometric distributions thereby frustrating the photometric function of the luminaire.
Additionally, the base of the conventional solid state bulb contains the relatively expensive drive electronics, and a commercial seller of such lamps must stock lamps of various brightness levels (e.g., 40 W, 60 W equivalents) to satisfy the differing needs of the consumers.
In the field of compact fluorescent lamps, there is usually a base which contains the electrical conversion electronics (ballast) and a twisted glass tube structure that is permanently attached to the base of the lamp. The life expectancy of the typical compact fluorescent lamp is about 5000 to 15,000 hours, and it is usually the failure of the fluorescent tube that signals the end of life for the lamp. Unfortunately, the electronic ballast in the base is usually still viable but because they are permanently joined, the entire lamp is usually thrown out and, in many cases, without regards to the toxic metals and other materials inherent with these lamps. This practice is further environmentally unsound since it is possible that the ballast in the base of the typical compact fluorescent lamp could conceivably last several times longer than the fluorescent tube it is powering.
What is needed is a new approach for a solid state lamp that can replace a variety of standard incandescent and compact fluorescent lamps having different wattages. Such a solid state lamp preferably allows adequate heat to be removed without significant added cost or added weight and overcomes other drawbacks of prior art solid state lamps and also significantly improves the environmental limitations of the prior art incandescent, compact fluorescent, and solid state lamps.SUMMARY
In one embodiment, a solid state lamp may replace a standard incandescent bulb having an Edison-type screw-in connector. The solid state lamp includes a base comprising an electrical connector, a power converter for converting the mains voltage into a suitable LED drive voltage, and a support area having a plurality of sets of receptacles for plug-in modules containing LEDs. Each plug-in module may be a flat module containing an array of LEDs connected in series, where the module mounts perpendicular to the surface of the base. The light emitted from a single module may be bidirectional.
Each module may produce light equivalent to a 20 W bulb. In one embodiment, there are three receptacles on the base arranged 120 degrees apart. The lamp can therefore produce sufficient lumens to replace either a 20 W, 40 W, or 60 W bulb. The user may purchase a single base and have the option for any of the three brightness levels.
Other embodiments of the modules may be wedge-shapes, were the LEDs are mounted on the outer wall of the wedge.
Other embodiments of the modules could also have wedge shapes that are optical structures where the LEDs are mounted in the lower extremity and the light is guided via total internal reflection upwards and extracted outwards in a desired pattern emulating a lamp.
In one embodiment, the modules are transparent or reflective planes, each side of a plane supporting one or more flexible LED strips for light emission in generally opposite directions. Each strip encapsulates a string of low power (e.g., 20 mA), bare LED dies without wire bonds. The strips are thin, allowing heat to be transferred through the surface of the strips to ambient air and to the planes. Therefore, there is a low heat-producing large surface area contacted by ambient air.
In one embodiment, to replace a 60 W incandescent bulb, there are a total of 12 LED strips affixed to the surfaces of three planes, each strip having 12 LEDs in series for generating a total of 800-900 lumens. The 12 strips are driven in parallel. The LEDs may be driven at a low current so as to generate very little heat, and are spread out over a relatively large bulb surface, enabling efficient cooling by ambient air.
Each module may have two or more electrodes for driving the one or more strips affixed to its surface.
By using unpackaged LED dies in the strips, and using traces in the strips to connect the dies in series, the cost of each strip is very low. Using bare LED dies in the strips, compared to packaged LEDs, reduces the cost per LED by 90% or more, since packaging of LED chips to mount them in a sealed surface mount package is by far the largest contributor to an LED's cost.
White light may be created by using blue LEDs in conjunction with a phosphor or combinations of phosphors or other light converting materials in either proximate or remote configurations. Light emitting dies other than LEDs may also be used, such as laser diodes.
Many other lamp structures are envisioned. For example, the strips may have sufficient mechanical integrity to not require being affixed to a rigid form. In one embodiment, a plurality of plug-in strips extends from a base and the strips are bendable by the user to have any shape and to produce a customized light emission pattern.
Another embodiment could also employ strips that could have asymmetric distributions on opposing sides, with one side offering the benefit of narrow emission as in a spot light and the other offering diffuse light emission. The combination of strips can be further mixed and matched at the user's discretion to provide for diffuse emission in some strips and for directional spot lighting from other strips such that the overall bulb can exhibit dramatically different photometric behaviours within a single unit. The benefits from such a construction completely free the user in terms of what is defined as a bulb, since the properties of many types of bulb can be engaged within a single unit thereby increasing almost infinitely the number of possible light distribution patterns that could be created.
Furthermore, the ability to vary distribution and correlated colour temperature or chromaticity is also afforded by this design since users could then elect to have for example, some strips that contain directional spots with low color temperature while adjoining strips could offer diffuse light emission at higher color temperature or another chromaticity.
The resulting solid state lamp has an efficiency that is much higher than an incandescent bulb for the same lumens output, and much less heat is generated. Additionally, since the LEDs are spread over a relatively large exposed surface, heat is adequately removed in any orientation of the lamp. Other advantages exist.
Many other embodiments are described.
Elements that are the same or similar in the various figures are identified with the same numeral.DETAILED DESCRIPTION
An AC/DC converter is housed in the base 10 for converting the 120V AC mains voltage to around 40 volts DC to drive the LED modules, described later.
The base 10 body may be formed of ceramic or other type of thermally conductive insulating material.
The top surface 18 of the base 10 is provided with multiple plug-in receptacles for receiving a plurality of LED modules.
In one embodiment, each module 26 generates light equivalent to a 20 W incandescent bulb. Any number of modules from one to six can be plugged into the base 10 to provide the desired amount of lumens. The light is emitted approximately 360 around the lamp due to the wide (e.g., Lambertian) light emission from each LED. Each module 26 may also include a reflector layer to further mix and spread the light output.
In one embodiment, the single base 10 can support a variable number of modules 26 to generate a selectable amount of light equivalent to an incandescent light bulb of 20 W, 40 W, 60 W, 80 W, 100 W, or 120 W. Due to the use of low power LEDs (e.g., 20 A) spread over a relatively large surface that is exposed to ambient air, there is no problem dissipating heat, unlike conventional LED “bulbs” using a few high power LEDs mounted on a flat substrate. Additionally, the arrangement of the modules 26 creates a 360 degree light emission that better emulates that of an incandescent or compact fluorescent bulb.
If there are a sufficiently large number of LEDs connected in series, the LEDs may be driven from the AC mains voltage without an AC/DC converter, reducing the cost of the lamp and the heat generated. Furthermore, high frequency types of AC conversion transformers may also be employed that generate lower AC voltages to also create suitable drive conditions for the LEDs. These compact AC conversion sources often operate at a high frequency beyond the flicker fusion frequencies or electrochemical response thresholds for human vision thereby eliminating any concerns for flicker that have plagued many prior art LED bulbs.
In recent presentations from the US Department of Energy, there is also the potential for the LEDs in the lamp to be driven directly from a DC grid within the luminaire or dwelling with the aid of current limiting active and/or passive devices. The incorporation of a direct DC grid system would be advantageous for safety and thermal purposes as the voltage to the bulb will likely be within the “Safe Extra Low Voltage” (SELV) regime where the added efficiency of not having to convert voltages and currents will result in significantly more efficient drive electronics and less damaging heat accumulation in the lamp.
The modules can take many different forms.
In all of the module forms, it is also implied in their designs that wiring choices for LEDs and distribution of LEDs and optical structures are advantageously free for adjustment such that light bulb optical distributions, flux outputs, chromaticities and many other variables are freely available in manufacturing and utilization to suit a variety of applications and luminaires.
The wedge-shaped modules 45 may be hollow to improve heat dissipation. The hollow wedges may be transparent to pass light from other wedges or bidirectionally emit light to increase the uniformity of light emission around the lamp.
Cathode conductors 66 are formed on the bottom substrate 60 and are bonded to the cathode electrodes of the vertical LEDs 64.
A top substrate 68 has cathode conductors 70 that are aligned with the cathode electrodes of the LED 64 and also make contact with the anode conductors 66 to connect the LEDs 64 in series. The area around each LED 64 may be filled in with a phosphor/silicone mixture to encapsulate the LEDs 64, or just silicone may be used as the encapsulant and the top surface of the top substrate 68 is coated with a layer of phosphor to create white light.
A thin layer of silicone or other adhesive may be applied on the top substrate 68 or bottom substrate 60, except where the conductors are located, to affix the substrates to each other and to fill in any gaps between the two substrates. Alternatively, lamination may be achieved by use of other adhesive materials, ultrasonic bonding, laser welding, or thermal means. A conductive paste or adhesive may be deposited over the cathode conductors 70 to ensure good electrical contact to the anode conductors 66 and LEDs' cathode electrodes. A phosphor tile or layer may be formed on the top substrate 68 for creating white light from the blue light emitted vertically from the chip 64. An optional reflective layer 58 is formed on the bottom substrate 60 for reflecting light toward the output surface.
Instead of the groove or cavity being formed in the bottom substrate 60, the groove or cavity may be formed in the top substrate 68, or partial-depth grooves or cavities may be formed in both substrates to account for the thickness of the LEDs 64.
If the LEDs are very thin, such as less than about 200 microns, the thickness of the LEDs may be accommodated by deformation of the substrates around the LEDs. The top substrate 68 may be heated and softened when laminating it over the bottom substrate 60 to conform the substrates to the LEDs 64 for adequate encapsulation.
At the end of each series string of LEDs, the anode and cathode conductors on the substrates must be able to be electrically contacted for connection to a current source or to another string of LED chips, whether for a series or parallel connection.
The interconnector 86 may also be a plating of the hole in the intermediate sheet 90 or a soft conductor paste that is injected into the hole, printed within the hole, etc.
The interconnector 86 may also be any of a variety of active or passive components as may be dictated by the drive and control circuitry. There are known to be many compact passive and active components (e.g., transistor switches) that can be produced in sufficiently small sizes that could be directed to use in place of the interconnector 86.
A phosphor layer or tile 98 may be affixed on the top substrate 94 over the LEDs 64 to convert the blue light emitted from the top surface of the LEDs 64 to white light. If the phosphor layer/tile 98 was large enough, then phosphor need not be used in the encapsulant.
The bottom substrate 80 may have a reflective layer either imbedded in it or on its bottom surface, as previously described, for reflecting light toward the light output surface. Optionally, internal reflectors 99 may be directed to reflect light upward.
In a related embodiment, the hole for the interconnector may be formed completely through the light sheet, then filled with a metal or coated with a metal. The hole may be formed using a laser, mechanical punch, or other means. The metal may be a printed solder paste that is reflowed to make electrical contact to the conductors formed on the substrates to complete the series connection. Extending the metal external to the light sheet will improve heat sinking to ambient air or to an external heat sink material. If the metal has a central hole, cooling air may flow through it to improve convective cooling.
It may be desirable for the light strips to provide bidirectional light rather than affix an LED strip to both sides of a module.
Lenses 110 may be formed over the LEDs 64 to control the light emission. A phosphor layer 112 is shown over the lenses 110 to produce white light.
Reflectors (not shown) may also be used to surround lenses 110 to provide for directed light emission similar to a reflector lamp.
It is also understood that the choice of lens, lens and reflector, or planar diffuse emission, or any other type of optical management can both be mixed on any one side of the sheet as desired or be directed be exclusively on one side such that each side of the sheet can have a different light distribution intensity pattern.
Many other types of light sources may be used for any of the modules described herein.
The lamp may have virtually any shape. By providing a common base and plug-in modules, only a single base needs to be purchased for a variety of possible brightnesses, chromaticities, and light distribution patterns. The resulting lamp emits light, especially using a dome diffuser, that better emulates an incandescent or compact fluorescent bulb, compared to prior art solid state lamps using high power LEDs mounted on a flat base. Cooling the LEDs using the present embodiments requires no large metal heat sinks. Other advantages exist.
The inventions can be applied to any form of lamp having any type of electrical connector. The lamps may run off the mains voltage or a battery. If a battery is the power supply, the selection of the number of LEDs in a strip (determining the voltage drop) may be such that there is no power supply needed in the lamp.
The various features of the lamps described herein may be combined in any way.
Having described the invention in detail, those skilled in the art will appreciate that given the present disclosure, modifications may be made to the invention without departing from the spirit and inventive concepts described herein. Therefore, it is not intended that the scope of the invention be limited to the specific embodiments illustrated and described.
1. A solid state lamp comprising:
- a base portion having an electrical connector for connection to a source of power;
- a plurality of modules, each module of the plurality of modules comprising multiple light emitting diodes (LEDs), and two opposing surfaces through which the module emits light; and
- a plurality of receptacles on the base portion configured to receive the plurality of modules and to provide drive current to the multiple LEDs in each of the plurality of modules,
- wherein each module of the plurality of modules has electrical connectors to connect to associated receptacles on the base portion, the receptacles supporting the modules when the modules are electrically connected to the receptacles,
- wherein the modules and base portion are configured to allow a user to select a number of modules to connect to the base portion and to operate the lamp with different combinations of modules to generate a desired light output from the lamp.
2. The lamp of claim 1, wherein the multiple LEDs of each of the plurality of modules are connected in series.
3. The lamp of claim 2, wherein the multiple LEDs in different modules of the plurality of modules are connected in parallel when the different modules are electrically connected to the receptacles.
4. The lamp of claim 1, wherein each of the plurality of modules comprises a strip of multiple LEDs, connected in series, mounted on a support structure.
5. The lamp of claim 1, wherein each of the plurality of modules is a flat plane on which the multiple LEDs are mounted.
6. The lamp of claim 1, wherein each of the plurality of modules comprises LEDs arranged along an arc.
7. The lamp of claim 1, wherein each of the plurality of modules is wedge shaped and emits light in an arc.
8. The lamp of claim 1, wherein the plurality of modules includes identical modules.
9. The lamp of claim 1, wherein the plurality of modules comprise cylinders having different diameters so that the modules of the plurality can be concentrically mounted on the base portion when connected to their associated receptacles, wherein at least an outer module passes light from an inner module.
10. The lamp of claim 1, wherein light is emitted 360 degrees around the lamp by the plurality of modules.
11. The lamp of claim 1, wherein each of the plurality of modules contains multiple bare LEDs encapsulated by substrates.
12. The lamp of claim 1, wherein each of the plurality of modules contains at least 10 LEDs connected in series.
13. The lamp of claim 1, wherein there are at least three sets of receptacles on the base portion for supporting at least three modules of the plurality of modules.
14. The lamp of claim 1 wherein the electrical connector is an Edison-type screw-in connector.
15. The lamp of claim 1, wherein the plurality of modules have electrodes that plug into associated receptacles.
16. The lamp of claim 1, wherein each of the plurality of modules comprises a group of LEDs, wherein each group comprises:
- a first substrate having first conductors;
- a second substrate having second conductors; and
- bare, unpackaged LED dies sandwiched between the first substrate and second substrate, wherein the first conductors and the second conductors connect the LED dies in each group in series.
17. The lamp of claim 1, further comprising a wavelength conversion material over the multiple LEDs of each of the plurality of modules to generate white light.
18. The lamp of claim 1 further comprising an AC/DC power converter in the base portion.
19. A method of controlling light output from a solid state lamp, the lamp comprising a base portion having an electrical connector to connect to a source of power, and a plurality of receptacles on the base portion to receive a plurality of modules, each module of the plurality of modules including (i) multiple light emitting diodes (LEDs), (ii) two opposing surfaces through which the module emits light, and (iii) electrical connectors to connect the module to an associated receptacle from among the plurality of receptacles on the base portion, the method comprising:
- supporting the plurality of modules, each module having electrical connectors for connection to associated receptacles on the base portion, the receptacles
- supporting, by the plurality of receptacles, the plurality of modules that are electrically connected to the plurality of receptacles; and
- plugging in any of multiple combinations of the plurality of modules into the plurality of receptacles to generate a desired light output from the lamp.
Filed: Feb 22, 2011
Date of Patent: Apr 2, 2013
Patent Publication Number: 20110163681
Assignee: Quarkstar LLC (Las Vegas, NV)
Inventors: Wilson Dau (Calgary), Louis Lerman (Las Vegas, NV), Allan Brent York (Langley), Robert Steele (Redwood City, CA), Jacqueline Teng (White Salmon, WA), George Lerman (Las Vegas, NV)
Primary Examiner: Douglas W Owens
Assistant Examiner: Minh D A
Application Number: 13/032,510